Anti-skid compositions and container material coated therewith



Feb. 3, 1959 E. E. LEPTIEN 2,872,094

ANTI-SKID COMPOSITIONS AND CONTAINER MATERIAL COATED THEREWITH FiledNov. 9, 1956 COATED VVh-H COLLOID/IL SILICA F in .1. AND

Ex TENDER 17:4 TEE/A L COA 11:0 VV/ TH COLLOID/u. SILICA Exrs/vame MATee/AL.

INVENTOR. ELMEI? E. LEFT/EN.

WMWMAM 147T ORNEKS United Stt ANT I-SKID COMPOSITIONS AND CONTAINERMATERIAL COATED TI-EREWITH Application November 9, 1956, Serial No.621,349

7 Claims. (Cl. 229-35) This invention relates to non--skid oranti-slipping compositions for application to container materials, par--ticularly cellulosic paper materials, including kraft bag stock,paperboard and the like. It also relates to cellulosic containers andcontainer materials of the above paper type having outer surfaces coatedwith said compositions. This application is a continuation-in-part of myapplication Serial No. 552,961, filed December 13, 1955.

While the novel compositions of the present invention are suitable fortreating a wide variety of paper container materials to enhance thesurface frictioning qualities thereof, for reasons of simplicity thefollowing description and discussion of prior art is directed to its usein connection with kraft paper bag material. In describing the containermaterial product of improved slip resistance,

reference is also made to kraft paper. It is to be understood, however,that the present invention is not so limit+ ed, but is applicable tosimilar paper materials such as paperboard, etc.

In the accompanying drawing, Fig. 1 is a perspective partly in sectionof a multiwalled cellulosic packaging container bearing printed matter,the outer wall of which is coated with discrete particles of theanti-skid composition of the present invention. Fig. 2-is an enlargedend view of a similar bag with a section thereof cut away to illustratemultiwalled construction, and with the exterior surface of the outerwall coated with the anti-skid composition of the present invention.

Perhapsthe simplest approach to the manufacture of a paper which hasmore than average resistance to slipping upon itself is the formulationof a rough finish paper. For many applications, however, such a roughfinish paper is not entirely satisfactory. For example, in the case oflarge multiwall bag containers, the surface of the rough finish paperwas not sufi'iciently slip resistant to prevent toppling of bags piledupon themselves in transit as well as in storage. Obviously, the lowerthe density of the contents of such a large bag, the greater thelikelihood of skidding and slipping when the bags are stacked. Althoughrough paper may be satisfactory in some instances, its surface has verypoor printing characteristics, e. g., the rougher the finish, the moreblotting or irregular spreading upon application of the ink, whichresults in printed matter unpleasant to the eye. Development of specialinks to solve the spreading problem has met with only limited success.

the use of non-skid inks, but printing characteristics are not muchimproved.

Because of its lack of resistance to slipping, smooth kraft paper,although presenting an excellent surface for the acceptance of printingink, is not ideally suited for multiwall bags. Recently, treatment ofsmooth kraft paper with dilute aqueous colloidal silica in the form of asol has resulted in a measurable improvement in its slip resistance. Ifthe paper is printed, the aqueous colloidal silica is generally appliedfollowing drying of the The frictioning qualities of the rough finishpaper have been still further improved by 2,872,094 Patented Feb. 3,i959 printing ink. Treatment with an aqueous sol containing 3% by weightor less colloidal silica is not satisfactory, since the slip resistanceof the finished bag tube is not superior to that of rough paper printedwith nonskid ink. At concentrations of 6% by weight silica in theaqueous sol, a paper having an acceptable non-skid surface is possible,but at the expense of considerable sticking in the paper rolls, and inthe case of multiwall bag stock, the interior tubes have been found tostick together in the tubing machine. This sticking is due topenetration of the treated layer of paper by the aqueous silica sol.Application at concentrations above 6% by weight silica in the treatingsol, caused opposed similarly treated surfaces of kraft paper to turnwhite when rubbed together. Furthermore, at concentrations above 6% byweight the silica has an adverse effect upon the ink, changing the colorthereof, for example, green ink is turned yellow. At these higher silicaconcentrations sticking is considerably more pronounced.

The use of sodium silicate solutions results in undesirable penetrationof the paper with resulting sticking, without appreciably improving thesurface frictioning qualities. In fact, solutions of sodium silicate arenot as effective in the latter respect as sols containing about 6%colloidal silica, and sticking is more pronounced.

In view of the foregoing limitations upon the use of colloidal silicaand particularly its property of penetrating the layer of paper treatedrather than depositing silica only upon the surface, compositionscontaining colloidal silica alone leave a great deal to be desired inthe preparation of a paper of improved resistance to slipping. Thepresent invention provides novel coating compositions which overcome theabove difliculties, permit deposition More specifically, there are nowprovided novel compositions containing colloidal silica as an activeingredient capable of imparting skid resistance to the surface of papersuperior to that produced by the application of a composition containingcolloidal silica alone. Smooth kraft paper surfaces treated with thepresent compositions are also more resistant to slipping than roughfinish paper printed with non-skid ink. The novel coating compositionscontain as essential ingredients a continuous phase, which is preferablywater, and disperse solids in the weight ratio of about 3 to 16 parts ofwater to one part of solids. The solids comprise colloidal silica and amaterial hereinafter designated as an extender, with the silica andextender each present in amounts between about 3 and 15% by weight ofthe composition. The extender is a very finely divided material orpowder which is chemically inert with respect to silica and thecontainer material to be treated. It comprises clay (hydrated aluminumsilicates) talc, diatomite, insoluble carbonates, insoluble magnesiumsalts and any of the naturally occurring materials employed as fillersor extenders in the printing ink and pigment arts, as well as mixturesthereof. Because of their abundance and ready availability, clays willusually be employed.

' The extender acts as a vehicle for carrying the silica particles tothe sheet or material treated, while also preventing any objectionablepenetration by the silica of the paper being treated, whereby the silicaand extender are very largely retained on the surface. Furthermore, thepresence of the extender provides a composition especially well suitedfor roller application to the finished paper or container stock. It hasbeen found that a constant flow of the novel composition can now bemaintained regardless of machine speed when applied by the roller, thusassuring a uniform coating on the paper. With colloidal silica alone,great difiiculty is encountered in maintaining a uniform flow in rollerapplication. While the present compositions may also be applied byspraying either to unshaped container material or to the finishedcontainer as a paperboard box or bag, the resulting coatirig willgenerally be found to be less uniform. In' addi tion, necessaryscreening precautions may be required to eliminate occupational hazardsfrombreathing air containing a high percentage of colloidal silicaparticles and finely divided extender. Following application of thenovel composition the treated surface is suitably dried or Containermaterial surface-treated with the compositions of the present inventionnot only possess surface frictioning or anti-slip properties superior totreated materials heretofore available, but also the colloidal silicaand extender deposited upon the surface of the material enhence itsresistance to soiling, provide a surface of improved printingcharacteristics, add luster to the paper and to the ink, and afford asubstantial measure of 'resistance to ink rub.

allowed to dry before the material is rolled or otherwise 111 Orderestablish improved p Iesistahce, tests contacted with it lf wereconducted on unprinted and printed smooth finish When the composition isapplied to a web by a roller, kl'aft P P The angle p Was similarly h 'hi the web running at h usual speed of a b as in each instance bymeasuring the angle of inclination at fed into a bag tubing machine, theroller, traveling at a Which uniformly loaded Sheets of P p Started toShde circumferential speed equal to that of the travel of the pthemselves- The angle was determmed for pp paper, can be made to pick upfrom a. pan sufiicient of unprinted, Pflhted t0 unprinted and PP fPfmted t0 the material and apply it to the web in Contact thereprintedsheets before and after treatment with the comwith whereby the desiredamount per i area ill he position of the present invention. The testswere carried distributed over the sheet. Furthermore, with the pres- Pemploying a f g chmPosltloh havlhg the follow ent compositions, theunexpected result is obtained that analysis y Welght? the coatingapplied to a'printed web adds substantially to P t the luster of theprinted areas, and despite the presence Water 89 of the clayor theequivalent, the legibility of the printing S10 6 is in no way interferedwith. Furthermore, the clay is Cl 5 adequately retained in place so thateven when two sheets bearing the coating are rubbed firmly together,there is The paper sheets were coated uniformly and the coated nochalking or whitening, such as would indicate resurface allowed to dry.moval of the silica and clay from the paper. The following table showsthe improvement in re- The novel compositions of the present inventionare sistance to slipping of the treated paper:

Angle of slip (degrees) Untreated Treated Paper Uuprlnted PrintedPrinted Unprinted Printed Printed to to to to o to Unprlnted UnprlntedPrinted Unprlnted Unprlnted Printed Regular Kralt Unprlnted ate so. a

Regular Kraft Printed 24.2 25.0 26.7 31. 9 29. 0 28. 5

preferably prepared by diluting to the desired degree a The novelcompositions containingpcolloidal silica and colloidal solution of.hydrated silica or a polymerized the extender material, which ispreferably very finely form of silicic acid, which does not contain anysignificant divided clay, as indicated above, may be applied to quantityof free alkali. In this latter respect at least the printed or unprintedpaper either by spraying or by starting silica material is to bedistinguished from alkali means of a roller. However, for high speedroller apmetal silicates for example, which are not employed. Theplications to a heavily printed kraft paper web as the silica is usuallyin the form of an aquasol, or an organosame is fed into a bag tubingmachine modification of aquasol. An aqueous product particularly wellsuited the coating compositions is desirable. Due to their nato thepreparation of the compositions of the present inture, most inks resistwetting by water with the result vention is Ludox manufactured by the E.I. Du Pont that the aqueous composition is disposed at random in deNemours, & Company containing about 30% by small droplets on the inked.surface, and deposition of weight colloidal silica, and having an Na Ocontent besilica and extender is thus restricted to the areas coveredtween about 0.09 and 0.11%.. Syton, the aqueous by these drops. In orderto increase the slip resistance of colloidal silica of approximately thesame concentration the paper surface, it is essential that a coating ofsilica manufactured by Monsanto Chemical Company may also and extendermaterial be deposited substantially uniformbe employed. Followingdilution of the sol with water, ly on the surface, whether the same beinked or not. the finely divided extender material .is dispersed withagi- Accordingly, it is Within the Scope of the Present invention tationthroughout the resulting sol, thus forming the antito reduce the surfacetension of the composition in order slipping composition. As indicatedabove, the solids in at he ink d r s may b r d nif rmly. Thi thetreating composition, amounting to about 6 to 30% is accomplished bymeans of a wetting agent. of its weight, comprise about 3l5% by weightcollodial Extensive tests indicated that a wide variety of inks, silicaand about 315 by weight finely divided exincluding those having a veryoily base, were most tender. The exact ratio of water to solids in thefinal easily and quickly wetted when the coating compositioncomposition, as well as the proportions of silica and ex- ContainedSmall q n i f IIOII-iOIIiC Wetting ag tender in the solids is determinedby the surface charac- Particularly the Complex Polyalkylene ellhelWetting teristics, thickness and the type of paper or other conagehts-These Compounds are in general P p by tainer material which is to betreated. In the case of reacting a Water-insoluble hydrocarbon havingone or smooth k f paper, the fo mula which produces the more reactivehydrogens with an alkylene oxide, for lowest acceptable increase in slipresistance is: water example, ethylene Oxide, as Set forth below, about92%, colloidal silica about 3% and extender mate- RH" mnCEh-CH; --t 12[onr-oHlo1mHm rial (clay) about 5%. For optimum improvement in slipresistance of this paper, compositions containing about 7 0 j to water,about 6 to 9% colloidal silica, and where n is the number of reactivebydrogens of com about 4 to 6% clay have been found quite satisfactory.75

pound R and m is the number of alkylene oxide groups required to reactwith n number of hydrogens. The Wetting agents which are preferred arethe complex nonionic polyethylene ethers, or polyethenoxy compounds,present in amounts between about 0.25 and 2% by weight of the totalcomposition. A particularly eifective wetting agent of this type isNeowet which is manufactured by Royce Chemical Company, Carlton Hill,New Jersey.

While incorporation of a wetting agent of the above type permitted rapidwetting of the inked surface and resulting deposition of silica andextender uniformly on the ink surface, a great deal of foaming wasencountered when the tuber was run at its normal high speed forprolonged periods. High roller speeds produced considerable agitation ofthe composition, causing it to foam and run over the sides of the press,even when only a very small quantity of wetting agent was employed. Inorder to counteract this undesirable characteristic of the wettingagent, the present invention contemplates the addition of a foamsuppresser or defoaming agent to the coating compositions. Materialsparticularly well suited to this application are the silicones, and moreparticularly the less viscous, e. g., about 1 to 1500 centistokes, fluiddimethyl polysiloxanes having the generic formula These materials arehighly efiective in eliminating foaming when present in the wettingagent-containing compositions in very low concentration, for example,between about 1 and 100 parts per million. Because of the dimculty ofadding such small amounts, the polysiloxanes are often present in excessof 100 parts per million. The excess does not appear to be detrimental.Since the dimethyl polysiloxanes are immiscible with water, anemulsifier is necessary when they are employed in the present aqueouscompositions. Suitable dimethylpolysiloxanes are available commerciallyas concentrated aqueous emulsions, and DoW-Cornings Antifoam AF hasproved very successful when added to the compositions of the presentinvention. The latter material consists of about 30% by Weight dimethylpolysiloxane, about 12 to 14% of an emulsifier (glyceryl monostearateand a polyoxyethylene monostearate), with the balance of the compositionbeing water.

The wetting agent and the foam suppresser are added to the aqueouscolloidal silica-extender composition in such small quantities that theWater content of the compositions aforementioned for optimum improvementin slip resistance is not altered appreciably. A preferred composition,in percentages by weight, for high speed roller application, withoutfoaming, to kraft bag stock having a large printed area on its surfaceis as follows:

The above formulation may of course also be applied to weight percentextender based upon the weight of the paper treated. However, it isdifficult to speculate upon the weight percent solids which will bedeposited upon lighter or heavier container material. It is safe to saythat the silica and extender are uniformly disposed upon the surfacetreated in a weight ratio very nearly equivalent to their ratio in theaqueous treating compositions.

I claim:

1. A composition for application to the surface of cellulosic containermaterials for imparting slip resistance thereto consisting essentiallyof about 3 to 15% colloidal silica, about 3 to 15% finely dividedextender material, a non-ionic, polyalkylene ether Wetting agent, anemulsified dimethyl polysiloxane foam suppresser, and the balancesubstantially water.

2. A composition as set forth in claim 1, wherein the finely dividedextender material is selected from the group consisting of clays, talc,diatomite, insoluble carbonates, insoluble magnesium salts and mixturesthereof. 3. A composition as set forth in claim 2, wherein said wettingagent is a polyethylene ether and is present in amounts between about0.25 and 2% by weight of the composition.

4. A composition for application to the printed surface of a kraft paperfor imparting slip resistance thereto consisting essentially of about 3to 15% colloidal silica, about 3 to 15% finely divided clay, about 0.25to 2% of a non-ionic polythylene ether wetting agent, at least 1 toparts per million of an emulsified dimethyl polysiloxane foamsuppresser, and the balance substantially water.

5. A smooth finished kraft paper bearing printed matter upon which therehas been applied an aqueous composition consisting essentially of about3 to 15% by weight colloidal silica, about 3 to 15% by Weight of finelydivided extender material selected from the group consisting of clays,talc, diatomite, insoluble carbonates, in soluble magnesium salts andmixtures thereof, a nonionic polyalkylene ether wetting agent, anemulsified di-. methyl polysiloxane foam suppresser, and the balancesubstantially water.

6. A composition for application to the surface of cellulosic containermaterial for imparting slip resistance thereto consisting essentially ofabout 3 to 15% colloidal silica, about 3 to 15% finely divided clay,about 0.25 to 2% by weight of a non-ionic wetting agent, at least 1 to100 parts per million of a silicone foam suppresser, and the balancesubstantially water.

7. A cellulosic container material of improved slip resistance for usein the manufacture of cartons, single wall bags, the outer wall ofmultiwall bags, and the like upon which there has been applied acomposition consisting essentially of about 3 to 15% by weight colloidalsilica, about 3 to 15% by weight of finely divided clay, I

about 0.25 to 2% by weight of a non-ionic wetting agent, at least 1 to100 parts per million of a silicone foam suppresser, and the balancewater.

References Cited in the file of this patent UNITED STATES PATENTS2,070,954 Nickerson -4 Feb. 16, 1937 2,415,752 Nanfeldt Feb. 11, 19472,420,475 Greger et al. May 13, 1947 2,643,048 Wilson June 23, 19532,787,968 Luvisi Apr. 9, 1957 FOREIGN PATENTS 59.295 France Ian. 6 1954UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No,2,872,094 February 3, 1959 Elmer E, L'eptien It is hereby certified thaterror appears in the printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 5,- line 57, for "Finely divided clay 0,5" read Finely dividedclay 5,0 column 6, line 28, for "polythylene" read polyethylene Signedand sealed this 19th day of May 1959.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Oficer Commissioner of Patents

5. A SMOTH FINISH KRAFT PAPER BEARING PRINTED MATTER UPON WHICH THEREHAS BEEN APPLIED AN AQUEOUS COMPOSITION CONTAINING ESSENTIALY OF ABOUT 3TO 15% BY WEIGHT COLLOIDAL SILICA, ABOUT 3 TO 15% BY WEIGHT OF FINELYDIVIDED EXTENDER MATERIAL SELECTED FROM THE GROUPE CONSISTING OFCLAYS,TALC, DIATOMITE, INSOLUBLE CARBONATES, INSOLUBLE MAGNESIUM SALTSAND MIXTURES THEREOF, A NONIONIC POLYALKYLENE EITHER WETTING AGENT, ANEMULSIFIED DIMETHYL POLYSILOXANNE FOAM SUPPRESSER, AND THE BALANCESUBSTANTIALLY WATER.